<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
         *{
            margin: 0;
            padding: 0;
        }
        div {
            width: 448px;
            height: 252px;
            margin: 0px auto;
        }
        .mask{
            position: relative;
            bottom: 256px;
            background: rgba(255,255,255,0.3) url(img/arr.png) no-repeat center;
            display: none;
        }
        .d1:hover .mask{
            display: block;
        }
    
</style>
</head>
<body>
    <div class="d1">
        <img src="img/tudou.jpg" />
        <div class="mask"></div>
    </div>
</body>
</html>